1. Field of the Invention
This invention is directed to filter networks including adaptive filters, in general, and to such networks which are arranged in serial connection, in particular.
2. Prior Art
There are many applications in today's technology wherein a wide band signal is generated, such as frequency modulation and spread spectrum communication signals. However, such wide band signals are often subject to interference imposed by outside sources. This interference can be either deliberate or inadvertent. For example, in a deliberate interference case, a hostile entity may impose a jamming signal in an attempt to disrupt and interfere with the wide band signal and the information portrayed thereby. In the case of an inadvertent interference, the wide band signal may be generated in an area where a radio transmitter or the like is in operation. However, in each case, the interfering signal is typically of narrower bandwidth than the wide band signal, especially in those cases, such as military applications, where the major wide band signal is submerged in the ambient noise signals to provide a degree of covertness.
In order to have the wide band signal serve some useful purpose, it is desirable to remove the narrow band interfering signals therefrom. In many cases, however, the method used to remove the narrow band interference typically results in a severely distorted and thereby, useless output signal. Consequently, new and improved techniques are continuously sought for effecting this operation.